1, 2. Oppress,depress, both having the literal meaning to press down upon, to cause to sink, are today mainly limited to figurative applications. To oppress is usually to subject (a people) to burdens, to undue exercise of authority, and the like; its chief application, therefore, is to a social or political situation: a tyrant oppressing his subjects.Depress suggests mainly the psychological effect, upon the individual, of unpleasant conditions, situations, etc., that sadden and discourage: depressed by the news. When oppress is sometimes used in this sense, it suggests a psychological attitude of more complete hopelessness: oppressed by a sense of failure.1. maltreat, persecute.

It is the due [external] restraint and not the moderation of rulers that constitutes a state of liberty; as the power to oppress, though never exercised, does a state of slavery. [St. George Tucker, "View of the Constitution of the United States," 1803]